Any tips on quickly working out Lowest common multiple,
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Any tips on quickly working out Lowest common multiple,
I was wondering if anyone has any tips/formula for working out Lowest common multiples, highest common factors etc. My daughter gets the right answer most of the time but takes a long while doing it.
Hi Silver29
The quickest way if the number can not be identified immediately is to use prime factors
i.e 2, 3, 5, 7, 11 etc
Any number can be written as a product of their primes
i.e 6 can be made by multiplying 2 x 3 (both prime numbers)
Work out prime factors as follows:
28
divide by 2
14
divide by 2
7
is a prime number
28 is 2 x 2 x 7
36
divide by 2
18
divide by 2
9
divide by 3
3
is a prime number
36 is 2 x 2 x 3 x 3
Place both sets of numbers closer together
28 = 2 x 2 x 7
36 = 2 x 2 x 3 x 3
The highest common factor is the highest number that goes exactly into both numbers.
The common factors in the example are 2 x 2
Therefore the highest common factor is 4
4 goes into 28, 7 times
4 goes into 36, 9 times
The lowest common multiple is the lowest number that both the numbers will go into.
For lowest common multiple we only count a common value once
28 = 2 x 2 x 7
36 = 2 x 2 x 3 x 3
The lowest common multiple is
2 x 2 x 3 x 3 x 7 = 252
28 goes into 252, 9 times
36 goes into 252, 7 times
Hope this helps
Regards
Mike
The quickest way if the number can not be identified immediately is to use prime factors
i.e 2, 3, 5, 7, 11 etc
Any number can be written as a product of their primes
i.e 6 can be made by multiplying 2 x 3 (both prime numbers)
Work out prime factors as follows:
28
divide by 2
14
divide by 2
7
is a prime number
28 is 2 x 2 x 7
36
divide by 2
18
divide by 2
9
divide by 3
3
is a prime number
36 is 2 x 2 x 3 x 3
Place both sets of numbers closer together
28 = 2 x 2 x 7
36 = 2 x 2 x 3 x 3
The highest common factor is the highest number that goes exactly into both numbers.
The common factors in the example are 2 x 2
Therefore the highest common factor is 4
4 goes into 28, 7 times
4 goes into 36, 9 times
The lowest common multiple is the lowest number that both the numbers will go into.
For lowest common multiple we only count a common value once
28 = 2 x 2 x 7
36 = 2 x 2 x 3 x 3
The lowest common multiple is
2 x 2 x 3 x 3 x 7 = 252
28 goes into 252, 9 times
36 goes into 252, 7 times
Hope this helps
Regards
Mike